Isolation and characterization of ELO1, a gene required for fatty acid elongation in Saccharomyces cerevisiae

A fatty acid elongation defective mutant was isolated from Saccharomyces cerevisiae by mutagenizing strains that were defective in fatty acid synthase (FAS) activity. Cells of the fatty acid synthase-defective strains can grow when supplemented with tetradecanoic acid (14:0) due to the presence of membrane bound elongation systems that can extend the 14-carbon fatty acid to longer-chain species. After mutagenesis and rescue on medium containing a mixture of 14:0, 16:0 and 18:0, cells were screened for their inability to grow on medium containing only 14:0. From 150,000 colonies, 4 stable isolates were identified, all of which appear to represent the same complementation group. Based on these analyses, the mutant isolates are all believed to carry the same defective gene elo1-1 (designated as elongation defective).; Gas chromatography of lipid extracts from cells of a fas2{dollar}Delta {dollar};elo1-1 mutant (DTY10m2) indicates that it fails to efficiently elongate (12, 13 or 14) carbon fatty acids. A gene disrupted fas 2{dollar}Delta{dollar}::LEU2; elo1{dollar}Delta{dollar}::HIS3 mutant incorporates 14 to 18-carbon fatty acids into membrane lipids, indicating that fatty acid transport is not affected by the mutation. Analysis of the ELO1 mRNA levels indicates that the gene is expressed in cells grown on fatty acid deficient medium. It is rapidly induced in wild type cells that are supplemented with 14:0 and is repressed when cells are supplied with 16 and 18-carbon fatty acids. Molecular cloning and sequence analysis of the ELO1 gene suggests that the encoded protein is a membrane bound polypeptide that contains at least 5 potential membrane spanning regions and a presumptive NADPH binding site. Homology searches of the yeast database indicate the existence of at least 2 other genes that share greater than 50% identity with ELO1. These genes are currently under investigation to determine their roles in fatty acid elongation.; The yeast ELO1 gene represents a novel pathway in the elongation of tetradecanoic acid (14:0) to that of hexadecanoic acid (16:0), distinct from that of fatty acid synthase.